1. Field of the Invention
The invention relates to a transmitter network comprising at least two transmitters having a like transmitter frequency and which transmit a like signal.
2. Description of the Related Art
Such a transmitter network is known from the technical article entitled "DAB--A new sound broadcasting system, Status of the development--Routes to its introduction" by G. Plenge in EBU Review no. 246, April 1991, Chapter 5.2.2, pp. 87-112.
When a conventional transmitter network is designed, for example, for broadcasting purposes, one is generally confronted with the problem that not enough channels are available for the signals to be transmitted. In that case one resorts to reusing frequencies, since under normal propagation conditions it is possible to receive in a certain area only one of the transmitters transmitting at a specific frequency and so no mutual disturbance need be expected. In such a conventional transmitter network, however, disturbances may nevertheless occur under special propagation conditions, such as, for example, tropospheric ducting.
In the transmitter network known from the above publication, a signal is transmitted with a like transmitter frequency via a plurality of transmitters, whereas a receiver can receive signals from different transmitters. As a result, a disturbance signal is developed having the characteristic of to an echo signal. This (undesired) echo signal is suppressed in the receiver by means of an echo canceller or by using a what is commonly referred to as a guard band in the time domain when the signal to be transmitted is actually transmitted. Consequently, it is possible for the received signal to be discarded in the receiver for a specific period of time during which the received signal is disturbed by the echo signals.
A great advantage of transmitter networks in which no more than a single transmitter frequency is used is that much fewer channels need to be available than when conventional transmitter networks are used having respective frequencies.
However, there may be a problem at the boundaries of the coverage areas of a plurality of such transmitter networks, because in that case signal received from a different transmitter network no longer has the features of an echo signal, and so the receiver cannot suppress the disturbing signals from a different network in an unqualified manner.